Optoelectronic components on an organic basis, for example organic light emitting diodes (OLEDs), are being increasingly widely used in general lighting, for example as a surface light source.
An organic optoelectronic component, for example an OLED, may include an anode or a cathode with an organic functional layer system therebetween. The organic functional layer system may include one or a plurality of emitter layer(s) in which electromagnetic radiation is generated, one or a plurality of charge generating layer structure(s) each composed of two or more charge generating layers (CGL) for charge generation, and one or a plurality of electron blocking layer(s), also designated as hole transport layers (s) (HTL), and one or a plurality of hole blocking layer(s), also designated as electron transport layer(s) (ETL), in order to direct the current flow.
Hitherto, in the case of organic light emitting diodes there have been two approaches for increasing the coupling-out of light: external coupling-out and internal coupling-out.
External coupling-out can be understood to mean devices used to increase the proportion of light which is coupled out from the substrate into emitted light. Such a device can be for example a film including scattering particles or a surface structuring, for example microlenses. The film can be applied to the outer side of the substrate, for example. Further possibilities may be a direct structuring of the outer side of the substrate or the introduction of scattering particles into the substrate, for example into the glass substrate. Some of these approaches, for example the scattering film, have already been used in OLED lighting modules or the high scalability thereof has been demonstrated. However, external coupling-out can have two significant disadvantages. In the case of external coupling-out, the coupling-out efficiency may be limited to approximately 60% to approximately 70% of the light guided in the substrate. Furthermore, the appearance of the organic light emitting diode may be significantly influenced in the case of measures for external coupling-out. By means of the applied layers or films, for example, a surface which is milky in its appearance and/or diffusely reflective may be formed in the organic light emitting diode.
Internal coupling-out can be understood to mean devices in which light is coupled out which is guided in the electrically active region of the organic light emitting diode, for example in the organic functional layer system and/or the transparent electrodes. In a conventional device for the internal coupling-out of light, a grating having a low refractive index can be applied on or over one of the electrodes of the optoelectronic component, for example an electrode composed of indium tin oxide (ITO). The grating includes structured regions including a material having a low refractive index. In a further conventional device for the internal coupling-out of light, a scattering layer can be applied above or on a transparent electrode, for example an indium tin oxide anode. The scattering layer includes a matrix composed of a polymer, in which scattering centers are distributed. The matrix has a refractive index of approximately 1.5 and the scattering centers have a higher refractive index than the matrix.
Internal coupling-out arrangements on the second electrode have the disadvantage that they are formed only at the end of the value creating chain, that is to say after the organic functional layer system has been formed between the first electrode and the second electrode. Conventional coupling-out arrangements in which the first electrode is formed on the coupling-out structure have the disadvantage that these internal coupling-out structures are complicated to produce and/or can adversely affect the durability of the component.